Dr. Tishkoff's DNA Project
Dr. Tishkoff studies genetics. That's the science that looks at how our
genes make us both different and alike. Genes are passed down through
families. Genes tell us how we are related to other people.
By studying the genes of people today, Dr. Tishkoff can tell if they were
ever related, even thousands of years ago. She can even tell if the people
of East Africa are related to people who live on other continents, such as
Europe and North America. Dr. Tishkoff has done other genetic research
before this project. In 2001, she made an important discovery about people
in Africa, Europe and Asia who are exposed to malaria, a disease that
kills more people than any other disease in the world. By studying their
genes Dr. Tishkoff found that many people had inherited gene mutations, or
changes, that help protect them from the malaria. The new thing that Dr.
Tishkoff found was that those gene mutations had originated in the
people's ancestors at the same time that malaria first began to spread
among humans. Dr. Tishkoff's discovery shows that disease can affect human
genetic history.
On this research trip to Africa, Dr. Tishkoff collected samples of genes
from many different people. Some of them still hunt for their food or
gather it from nearby plants and trees, as their ancestors did thousands of
years ago. They are called hunter-gatherers. Others raise their own food.
The people Dr. Tishkoff worked with spoke many different languages. "We
found people speaking all of the major language families present in Africa
in the areas we visited," says Dr. Tishkoff.
Two groups, the Hadza and the Sandawe, who live in East Africa, speak
languages made up of clicking sounds. These languages are classified as
Khoisan languages. Dr. Tishkoff hopes to learn whether the Hadza and the
Sandawe share a recent common ancestry with the other Khoisan speakers in
southern Africa, such as the !Kung San. Some scientists think the !Kung San
people may have originated in East Africa, then migrated to southern
Africa.
Dr. Tishkoff speaks English and some Kiswahili. Translators helped her
communicate with people who spoke other languages. Before Dr. Tishkoff left
the University Maryland, she did a lot of set-up work with other
researchers in Africa. Many of them want to help her find answers about the
past of their African ancestors.
The people Dr. Tishkoff met also look very different from each other. Some,
such as the Maasai, are very tall. Others, including the Hadza, are very
short. Dr. Tishkoff says "We don't think the Maasai and Hadza share a
recent common ancestry. We are studying the Maasai and other neighboring
tribes who speak many diverse languages to study East African genetic
diversity and to learn more about East African population history and
modern human origins."
Some other groups of people that Dr. Tishkoff studied include the Datog,
Gogo, Burunge, Turu, Iraqw, and Isanzu.
Facts on DNA and Genes
"There's a lot of evidence that modern humans had their origins in East
Africa," says Dr. Tishkoff. "I got DNA (click to link to below) samples
from people who were probably descended from some of the earliest people in
Africa. I'm hoping the information I find will give us more clues about who
our ancestors were and how they moved around."
DNA is short for deoxyribonucleic acid. This is the chemical that genes are
made of. DNA is found in blood, skin and other body fluids.
We get our genes from our parents. Genes are the part of our cells that
give us the color of our eyes. They decide how tall we will be or whether
we have curly hair or straight hair. Genes determine if we will get some
diseases.
Dr.Tishkoff collected almost 600 samples of DNA, which is present in many
parts of the body. These samples were collected from blood and from
scrapings of cells from inside people's cheeks "We never had problems
getting both blood and cheek cells," says Dr. Tishkoff. "We carefully
explained our study to them and collected samples only after they gave us
written informed consent."
Dr. Tishkoff and her team traveled in airplanes when they traveled across
Africa. But other times the only way they could get into remote areas was
in a Land Rover vehicle. The team camped out with tents and sleeping bags
in some places.
Dr. Tishkoff had to be creative when she was designing her research.
Because it's so hot where she was, she had to figure out a way to keep the
blood samples from being destroyed in the heat. She decided to take a
machine called a centrifuge, which separates white blood cells from red
ones. The white cells contain the DNA. Once the white blood cells were
isolated as small pellets, she added a buffer to preserve them. The pellets
were then stored and brought back to the United States.
Now that Dr. Tishkoff is back at the University of Maryland, she and her
team will isolate the DNA from the white cell pellets in her laboratory.
She'll compare the genes of the different people who gave her DNA samples.
By looking at little pieces of the DNA, she will learn the history of the
genes. If people have some of the same genes, it could mean they are
descended from the same ancestors. (Dr. Tishkoff says) "We use PCR
(polymerase chain reaction), gel electrophoresis and DNA sequencing using
an automated ABI 3100 capillary sequencer to find genetic variation that
can be used to trace the history of the genes and of the populations.
Frequently Asked Questions
Doing research in Africa was different from doing it in College Park in a
modern laboratory that has electricity and high tech equipment. Dr.
Tishkoff had to figure out a lot of things before she left for Africa.
How did she get to remote places?
She drove a Land Rover.
How did she get power to equipment like her centrifuge?
Dr. Tishkoff explains. "One of the centrifuges was run off of the car
battery. For the second one, we tried to work at clinics and mission
hospitals that either had electricity or generator power."
How did she power her computers?
With solar panels that use sunlight to make energy.
Dr. Tishkoff and her lab assistant needed a form called a visa to travel in
the different countries. How did she get them? She made personal visits to
the countries' embassies in Washington, D.C.
(Dr. Tishkoff says) "I also had to get research permits from the Tanzanian
government. I wrote a proposal that was carefully reviewed and accepted by
a panel of medical doctors and by officials at the Tanzania Center for
Science and Technology."
Grants
Research like Dr. Tishkoff's costs a lot of money. Many organizations make
research like this possible by giving money, called grants, to scientists.
Dr. Tishkoff had to write several grant proposals that described her work.
She won grants from the National Science Foundation, the Wenner Gren
Foundation and the Leakey Foundation, which helps scientists study
hunter-gatherer civilizations.
